Setting MTU when only a LAGG exists?

[BlindOracle]

Dear community,

a week ago I got my new Server for installing FreeNAS. The server has two 10G NICs, ixl0 and ixl1. So far so good, my plan was to put both interfaces into a LAGG and configure several different VLANs, for Management, Storage, etc. Right now I'm expiriencing an issue that when I try to set the MTU to 9000 for each member via WebUI, the immediately reboots and throws away all interfaces.
So I'd like to know how I can set the MTU for each LAGG member on command prompt that it will stay persistant.
I read several articles on the net and most of them tell to put the network config in /etc/rc.conf.
Sadly on FreeNAS 11.2-RC2 this does not work for me, well, as there is absolutely no network parameters in that file, I didn't want to break it.

Thanks very much in advance!

Blindy

 

[Chris Moore]

I read several articles on the net and most of them tell to put the network config in /etc/rc.conf.
Sadly on FreeNAS 11.2-RC2 this does not work for me, well, as there is absolutely no network parameters in that file, I didn't want to break it.

You are using the RC (Release Candidate) version of FreeNAS, so some things may not work properly. It sounds like you found a bug. You should file a bug report.
You might also want to contemplate using the 11.1-U6 version of FreeNAS as it is potentially more likely to work for you.
If you would also include the details of your system per the following guide:
https://forums.freenas.org/index.php?threads/updated-forum-rules-8-3-16.45124/

 

[BlindOracle]

Thanks. I'll file a bug report.
My further question is, if the pool I created on 11.2-RC2 would work with version 11.1-U6?
Is it backwards compatible and could I import it?

Thank you

 

[kdragon75]

So I'd like to know how I can set the MTU for each LAGG member on command prompt that it will stay persistant.

You can't. Most settings are configured at boot time based on the FreeNAS configuration file. This means anything done outside the UI will get undone with updates and possible even on every reboot. You would need to add startup commands/scripts via the GUI.

 

[kdragon75]

Remember FreeNAS is FreeBSD but tweaked into an appliance, not a normal OS install.

 

[jgreco]

Also it's worth noting that stacking things such as LAG, VLAN, and MTU, each of which are moderately twitchy on their own, because of all the various hardware implementations, etc., turns into a potential charlie foxtrot of issues when stacked on top of each other, ranging from poor performance (such as when hardware offload isn't enabled because of some incompatibility) to outright network stalls.

https://forums.freenas.org/index.php?threads/jumbo-frames-notes.26064/

You're much better off ignoring jumbo. Modern gear and network cards support swimmingly awesome offload features that make a lot of the things jumbo was designed to address irrelevant. Trying to maintain a network with jumbo means you may run into device or driver issues on every single device attached to that network. You are exercising code paths that are much less used than typical ethernet. In FreeBSD, for example, jumbo traffic runs through a different set of buffers with a different allocation strategy, which often needs to be manually tuned to avoid network stalls.

The trick for the MTU for the LAG members is to change "up" to "up mtu 9214" (or whatever the physical device max MTU is), and then specify the correct MTU for each member vlan. Failing to do this will cause some device drivers to drop the vlan tag especially if you are running through multiple layers of stacked virtual interfaces.

It's probably worth observing that I gave you a warning before I gave the answer...

 

[Chris Moore]

Thanks. I'll file a bug report.
My further question is, if the pool I created on 11.2-RC2 would work with version 11.1-U6?
Is it backwards compatible and could I import it?

Thank you

Yes, there are new feature flags in the newer version of ZFS but until you use those features, it still has backwards compatibility.

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